1. Field of the Invention
This invention is directed to a method of contraception that provides for the reduced level of estrogen in the initial and final phase of a quadraphasic estrogenic/progestogenic contraceptive regimen without compromising contraceptive efficacy or cycle control. The invention is also directed to a quadraphasic contraceptive kit that may be used to practice the method of the invention.
2. Related Background Art
Contraceptive compositions containing both estrogenic and progestogenic compounds are well known. The progestogenic component of the composition is primarily responsible for the contraceptive efficacy of the composition, while the estrogenic component is employed to reduce undesired side effects, such as breakthrough bleeding or spotting.
The earliest of these estrogenic/progestogenic contraceptive compositions contained a relatively high level of estrogenic component. A constant goal, however, has been to reduce the estrogenic potency of such compositions without reducing contraceptive efficacy and increasing undesired side effects. As described in U.S. Pat. No. 5,888,543, in an attempt to achieve this goal, numerous regimens have been developed in which the progestogen/estrogen combination is administered in a monophasic regimen (fixed dose) or as biphasic or triphasic regimens (varied dose).
A particularly advantageous technique for reducing total estrogenic administration is described in U.S. Pat. No. 4,962,098. This describes a triphasic method of contraception using a progestogen/estrogen combination in which the amount of estrogen is increased stepwise over the three phases. The first phase is 4-7 days, the second phase is 5-8 days and the third phase is 7-12 days. Preferably, the administration of the contraceptive compositions for the three phases will be 21 days followed by a 7 day placebo period. For all three phases the progestogen is 0.5 to 1.5 mg of norethindrone acetate, while about 10 to 30 mcg of ethinyl estradiol is used in the first phase, about 20 to 40 mcg of ethinyl estradiol is used in the second phase and 30 to 50 mcg of ethinyl estradiol is employed in the third phase.
DE 4313926 discloses a 4-phase contraceptive regimen that requires an estrogen and a progestin in the first three seven day phases and an estrogen in the fourth seven day phase. The progestin is only given for 21 days of a 28 day cycle. In addition, when the estrogen is ethinyl estradiol it is suggested that the concentration is stepped down from the phase two composition to the phase three composition in an attempt to mimic a woman's physiological cycle.
There is a continuing desire, however, to further reduce the amount of estrogenic component in an estrogenic/progestogenic composition with continued contraceptive efficacy while avoiding undesired side effects. This invention uses a low level of estrogen in the first phase and replaces the traditional placebo phase with a low level of estrogen to obtain follicular suppression and reduce the potential for endogenous estrogen production.